"Building the space station is not an ordinary construction job. It's very different, and it's different from building a house or a skyscraper, in that we're working in a very hostile environment, a very isolated environment. So, first of all, we're not as efficient working in these big, bulky spacesuits. We're time-constrained, up to eight hours at a time. We're constrained on the amount of tools and weight we can carry to space. So there it's somewhat unique.

"But part of the problem is, we have to have it all figured out before we show up in space. It's got to be all figured out, while on a construction site, if you're building a house and you cut a two-by-four to a certain length and you go to install it and it doesn't work, well, it might be a little inefficient, but basically you toss that board, you go cut another one, and you're off and running. If we show up in space, and now that piece that we're putting on doesn't fit, we're out of luck. That may have just delayed the next series of missions. We may have to add another mission now to bring up the right component, because they're all linked. So it's very complicated."